The present invention relates to the removal of a solder mounted electronic component on a surface. Solder mounted electronic components are typically used in close proximity to other components on the surface, such as a substrate or printed circuit board. When an electronic component fails it often becomes economically necessary to replace the bad device rather than replace the entire substrate. But this removal and replacement operation needs to be done without damaging other components in close proximity to the damaged device.
There are numerous conventional methods for surface repair where the solder is heated and the device removed from the molten solder. For instance, heating by means of a hot gas is described in U.S. Pat. No. 4,813,589 to Palmer et al. where a tube allows hot air to be directed from an external heat source to a component on a circuit board to be removed without permitting heat to flow to adjacent components, as well as protecting the chip from heat by placing a vacuum suction cup on top of the chip. Heating by means of heated blades is described in U.S. Pat. No. 4,614,858 to Vial where a desoldering tool contains heater bars shaped to contact the solder terminations to be desoldered as well as grasp the component to be removed. These conventional techniques have the drawbacks of leaving the reworked site on the substrate with uneven amounts of solder, leaving varying amounts of brittle intermetallic compounds and oxides that can lead to poor soldering joints of the replacement devices, and other reliablility problems. Further, the adverse effects of uneven solder thickness and intermetallic compounds become acute when the device lead center lines are less than about 0.020 inches, since at these dimensions the total volume of solder is small and the effect of thickness variations and intermetallic particles is great. Additionally, with conventional repair methods the leads that are broken and not attached to electronic components will often remain on the substrate after the electronic components are desoldered and removed. It may then be necessary to attempt to remove the broken leads manually with tweezers and a soldering iron. This manual removal is time consuming and can also result in damage to the substrate or nearby components.
There exists a need for removing a solder mounted electronic component and any broken leads from a multicomponent module in a single step while leaving a minimal amount of solder and intermetallic particles on the module surface, particularly for components with outer lead bonds having center lines spaced less than 0.020 inches.